The inventions relate to a sheath or catheter that has an expandable distal end.
In many minimally invasive medical procedures, an introducer sheath or catheter may be placed in a vessel to gain access to a site within a body for a diagnostic or therapeutic procedure. Sheaths and catheters are used as conduits to pass surgical instruments, implantable devices, or biological matter, such as clots, tissue samples, or other matter. The inner diameter of the sheath is designed as large as possible for the surgical instrument, implant device, or tissue sample to pass through it. It is generally desirable to minimize the outer diameter of the sheath and maximize the inner diameter of the sheath. A small outer diameter is desired to minimize the size of the hole at the insertion site. A smaller outer diameter also provides less disruption to the circulatory pathway. Since the outer diameter may be minimized and the inner diameter may be maximized, the thickness of the wall of the sheath could lack sufficient column strength for insertion into a blood vessel or other circumstances with longitudinally applied forces.
Medical devices that are implanted may require removal from the body or repositioning within the body. The device that is to be removed may be a temporary implant which has performed the desired diagnostic or therapeutic function. Alternatively, a device may be classified as a permanent implant but may require removal for some other reason. Sometimes devices need to be repositioned in the body. One way of repositioning a device is to pull the device back into a catheter (or push the catheter around the device) so that the device is disposed within the catheter. Then the device is repositioned to a desired delivery location and then deployed. The devices that are removed or repositioned may not collapse into a reduced profile configuration easily or completely.
Because the devices may not collapse completely or in a suitable orientation it may be difficult to reconstrain the device in a catheter. Specifically, this difficulty may be compounded by the material that is used to construct the catheter. The catheter walls are optimally designed to be as thin as possible while having sufficient column strength for proper operation. A material commonly selected for the construction of catheters typically has high stiffness or rigidity. The same material properties that are desirable in the construction of the catheter may make the withdrawal of an implant or tissue more difficult because a catheter constructed of a stiff material will not expand to accommodate a device that is being reconstrained after deployment. This can make it awkward to pass surgical instruments, implantable devices, and tissue samples either in or out of the sheath tip.